1. Field of the Invention
The present invention relates to a module board and a method of forming the same. More particularly, the present invention relates to a integrated module board, with a structure similar to a cavity-down plastic ball grid array (CD-PBGA) substrate or a substrate having various cavities, in which all kinds of chips and components are embedded or mounted onto the module board.
2. Description of the Related Art
Electrical packaging, including attachment of IC chips, electrical connections of circuits, sealing, assembly of a circuit board, system integration and product packing, integrates IC chips with essential components to achieve electric communication, circuit-signal communication, heat-dissipation path, loading capability and protection. In general, electrical packaging technology is classified into four fabricating levels. In the first level, electrical connections of circuits are completed on a substrate on which IC chips are fixed, and then the substrate is encapsulated to become a packaging body. In the second level, the packaging body is integrated to a circuit board with other electrical components. In the third level, several of the circuit boards are fabricated on a main board to serve as a sub-system board. In the fourth level, several of the sub-system boards are combined to complete an electrical product.
As the integration grade of IC chips on the substrate increases, the pin number of IC input and IC output does also, resulting in a requirement to develop a packaging substrate having a high-density arrangement of IC chips. For example, with a cavity-down plastic ball grid array (CD-PBGA) substrate, the IC chip is fixed in a cavity of the substrate, and is then electrically connected to bonding fingers on the substrate by an Au-wiring bonding process, and the CD-PBGA substrate is then placed on a circuit board in which the IC chip positioned in the cavity is allowed to attach to the circuit board. Furthermore, a heat-dissipation device is installed over the CD-PBGA substrate, and passive components are placed on the circuit board by an additional assembly process.
This process encounters the following problems. First, the packaging of IC chips, the assembly of passive components' surface mount technology (SMT) must proceed individually, resulting in a lengthy procedure, low yield, and high product costs. Second, since the assembly of passive components and the SMT cannot be integrated at the same packaging level, it is impossible to reduce the product to a desired thickness. Third, in order to achieve heat dissipation, a heat sink/fan and an electro-magnetic interference (EMI) shielding sheet must be further provided on the main board to enhance the electrical performance, also causing increased costs. Fourth, since the IC chips, the passive components, and the heat-dissipation device cannot all be integrated on the same substrate during the same packaging level, the circuit route of the product layout is extremely long, interfering with electrical properties.
Thus, a method of integrating the IC chips, the passive components, and the heat-dissipation device on a module board during the same packaging level to solve the aforementioned problems is called for.